Abrothallus boomii is a species of lichenicolous fungus in the family Abrothallaceae.

[1] Found in Portugal, it was formally described as a new species in 2015 by Ave Suija and Sergio Pérez-Ortega.

The type specimen was collected north of Ervas Tenras [pt] (Beira Alta Province) in a pine-oak forest along a vineyard, where it was found growing on the thallus of a Nephroma lichen.

The species epithet honours Dutch lichenologist Pieter van den Boom, "author of a long list of research articles and indefatigable collector of lichens and lichenicolous fungi".

[2] Compared to other Abrothallus fungi that grow on Nephroma, Abrothallus boomii differs in that its asci contain six spores, its pycnidia are semi-immersed, and its hyaline conidia typically measure 7–10.5 by 5.5–8 μm.